2D PCMRI Segmentation

The 2D PCMRI data were processed using the software Segment v2.1 R5960 (http://medviso.com/products/segment).12 A region of interest (ROI) covering the vessel was manually outlined in the image, considering both the magnitude and the phase image. The ROI size was kept constant through all timeframes, with a strategy to segment with a slightly oversized ROI13 that included all pixels that had a flow signal during any of the timeframes. For each artery, flow rates from the 2D PCMRI were determined as the mean flow over the 32 timeframes. Both 2D and 4D data were eddy current‐corrected.